Glancing angle deposition of helical manganese oxide nanostructures on the glass substrate and study the optical nonlinearity by Z-scan technique

Abstract

Helical manganese oxide nanostructures have been deposited on glass substrate by glancing angle deposition along with electron-beam evaporation technique. X-ray diffraction analysis, FESEM images, and FTIR spectroscopy confirmed the successful growth of the nanostructured thin film. The surface morphology and roughness of the deposited helical manganese oxide thin film were considered using the 2-D and 3-D AFM images. The optical constants along axes a, b, and c have been calculated from the effective medium approximation of Bruggeman. The refractive indices were found to be equal for helical manganese oxide nanostructures along a- and b-axes and greater than the refractive index along c-axis at λ < 600 nm; while these results are reversed for wavelengths greater than 600 nm. The same variations were observed for the extinction coefficients. The Z-scan measurements under continuous-wave (CW) laser irradiation at 532 nm showed a positive sign for both the nonlinear absorption coefficient and nonlinear refractive index of nanostructured helical manganese oxide demonstrating the attendance of induced absorption process and self-defocusing phenomena, respectively. We computed a 3rd-order nonlinear optical susceptibility, χ(3), equal to 0.042 esu that suggests the glancing angle deposited helical manganese oxide nanostructures with a strong nonlinear optical response can be a good candidate to develop nanophotonic devices.